Some photos of the chainline on the Rudy Fat, although this bike is setup with a single front ring you can see it will clearly take a double without tyre/chain rub. The spec is a Zee chainset with 32t absoluteBLACK chainring, 11-34 cassette, Northpaw 29+ rim with Knard 29x3" tyre at 120tpi @15psi

How Fat can you go on the Fat Race? Here are some images of the chainline. Small chainring to larges sprocket at the back. Component break down, Fat Race titanium frame with 100mm english thread bb, e13 trs double, Surly Nate 120tpi tyres on Marge lite rims